// Resize
$thumb = imagecrop($source, ['x' => 830, 'y' => 330, 'width' => 115, 'height' => 30]);
// Filter
imagefilter($thumb, IMG_FILTER_GRAYSCALE);
imagefilter($thumb, IMG_FILTER_BRIGHTNESS, +50);
imagefilter($thumb, IMG_FILTER_CONTRAST, -50);
As a result I got at least a result: 39984
Its still not correct, but better than no identification of any letter...
How can I improve?